More than £500,000 was passed to the Prince of Wales's Duchy of Cornwall estate in the last financial year from people who passed away with no will or living relatives.
Under centuries-old powers known as bona vacantia – the legal term for ownerless land – all unclaimed property belonging to someone who dies in Cornwall automatically passes to the Duchy, which is owned by the Prince of Wales.
The powers date back to the creation of the Duchy of Cornwall estate in 1337 by King Edward III. The estate was created to provide an income for the King's son and heir, Prince Edward, otherwise known as The Black Prince, who became the first Duke of Cornwall.
The Prince of Wales is not entitled to the proceeds or profit on the sale of estate assets, but receives the annual income which they generate.
A total of £552,000 was passed to the Duchy throughout the 2011/12 financial year under the law. Since 2006, the amount adds up to £1,019,000.
The money received through the law is donated to a selection of charities through the Duke of Cornwall's Benevolent Fund, minus an amount for "ex gratia payments and other associated costs" – which accounted for £86,000 last year.
The Benevolent Fund received £450,000 last year, while £154,000 was held back to meet the cost of any future claims on currently unclaimed properties.
The revelation of the ancient law's profitability comes amid heightened scrutiny of the Prince's estate. Anti-royalist campaigners last week launched a campaign demanding the land be handed over to local people.
Anti-monarchy group Republic last night called for the Duchy of Cornwall to be taken into public hands. "The money made from unclaimed property in Cornwall should go where it does everywhere else in the country. It should go to the Treasury and into public funds to be spent on public services," said Graham Smith, Republic's CEO.
A Duchy of Cornwall spokesperson said: "The Prince of Wales decided almost 40 years ago that the bona vacantia funds should be given to charity."